1. Field of the Invention
The present invention relates to a wiring board receiving plate used in connecting a wiring board or electronic component to a different wiring board having an electronic component mounted thereon and further to a connection device and method of a wiring board using the receiving plate.
2. Description of the Prior Art
In mounting a semiconductor device on a wiring board, for example, the flip-chip mounting method for mounting it on the wiring board in a so-called face-down state has been proposed and, for electrical connection between electrodes and for physical fixation of the semiconductor device, an anisotropic conductive film (ACF) has been used. The anisotropic conductive film has conducting particles dispersed in a binder resin serving as an adhesive agent, is sandwiched between an electrode on the wiring board and an opposite electrode of the semiconductor device and is heated and pressed to crush the conducting particles between the electrodes, thereby attaining the electrical connection between the electrodes. Since the conducting particles at portions provided with no electrode are maintained in a state of being dispersed in the binder resin and kept in an electrically insulated state, the electrical continuity is attained only at portions provided with the electrodes.
A method for mounting a semiconductor device using the anisotropic conductive film comprises disposing the semiconductor on a wiring board having the anisotropic conductive film attached thereto, using a thermal compression bonding head to press the semiconductor device while heating the anisotropic conductive film, thereby crushing the conducting particles between the electrodes and hardening the anisotropic conductive film to thereby subject the semiconductor device to thermal compression bonding. In the thermal compression bonding, as disclosed in Patent Document 1 as JP 10-256311 A, chip parts different in height are mounted in a lump through heating and pressure application in the presence of a buffer layer.
In recent years, the mounting method using the anisotropic film has been applied not only to mounting of electronic component, but also to connection of a flexible printed circuit (FPC) board to a motherboard substrate. In connecting a flexible printed circuit board drawn out of a liquid crystal display (LCD) panel or CMOS IC to a motherboard substrate of a mobile phone, for example, connection by soldering or a connector has mainly been used heretofore. However, in association with equipment lightweight, thin and small in size, connection by the anisotropic conductive film tends to be increasing. The connection by the anisotropic conductive film has various merits of realizing a small size and narrow pitch with ease, enabling cost reduction, enabling elimination of disconnection by impact and enabling use of a lead-free structure, for example.
On the other hand, adoption of the connection by the anisotropic conductive film has a demerit of requiring the rear surface of pressure bonded portions to be flattened. In the connection by the anisotropic conductive film, uniform pressure has to be applied to terminals and, in the case of connecting a flexible printed circuit board to a motherboard substrate, for example, no electrical component can be mounted in the vicinity of the rear surface of the connection portion of the motherboard substrate. This is because, when performing the thermal compression bonding, with the portion having mounted the electronic component supported on the rear surface side of the motherboard substrate, there is a possibility of entailing problems of applying uneven pressure, exerting an excessive load on the mounted electronic component and consequently damaging the electronic component.
In this case, mounting of the electronic component on the motherboard substrate is subjected to restraints including a requirement that the component be disposed in consideration of the connection by the anisotropic conductive film and, therefore, a problem of lowering the component-mounting area ratio is imposed.
In order to eliminate the above problems, the side of the receiving plate of the motherboard substrate has to be somewhat devised, and the invention described in Patent Document 2 as JP 2001-15908 A is one of the inventions having such a new twist. In Patent Document 2, disclosed is a method for mounting a circuit board comprising disposing on a substrate-retaining member a circuit board having a circuit component mounted on the rear surface thereof and mounting a signal input/output member on the front surface of the circuit board by thermal compression bonding that is performed while retaining the circuit board on an outer peripheral region of the circuit board and a region of the circuit component corresponding to the outer peripheral region.
In addition, it is also proposed that a component is mounted on the motherboard substrate having an electronic component mounted on the rear surface thereof by heating and pressure application in the presence of a buffer layer, similarly to the invention described in Patent Document 1. In Patent Document 3 as JP 11-354588 A, for example, disclosed is a method for bonding an electronic component provided with a bump for supporting pressure loads in a bonding process dispersed on a substrate supporting body that directly supports the lower surface of a substrate and on an elastic body that elastically supports an electronic component which has already been mounted on a surface opposed to the surface onto which the electronic component provided with the bump is bonded.
In the supporting structure of the invention described in Patent Document 2, however, since only the surroundings of the wiring board and mounting component are supported, it is difficult to stably support the wiring board and problems of flexing the wiring board at the time of thermal compression bonding, damaging the wiring board and applying uneven pressure to the wiring board to induce bad connection will remain. In addition, an increase in number of electronic components to be mounted on the wiring board makes the structure of the substrate-retaining member complicated and necessitates great equipment investment. These are also problematic.
What is conceivable to eliminate these problems is to use a buffer layer (elastic body) as described in Patent Document 3, for example, to support the component-mounting surface of the wiring board. Though this is somewhat expected to exhibit effectiveness to some extent, since the substrate-supporting body that supports the outer peripheral portion can only supports the lower surface of the substrate, it is difficult to realize a stable support state similarly to the invention described in Patent Document 2. In addition, since only the electronic component that has already been mounted is supported on the elastic body at the position on which pressure loads are actually exerted, excessive load is added consequently to the already-mounted electronic component. Particularly, when the difference in mounting height of the electronic components to be mounted is large, it is difficult to uniformly applying pressure even in the presence of the elastic body and to completely eliminate damages of the already-mounted electronic components.
The present invention has been proposed in view of the conventional state of affairs and the object thereof is to provide a wiring board receiving plate capable of realizing uniform thermal compression bonding relative to even a wiring board having an electronic component mounted on the rear surface thereof, eliminating bad connection in the substrate connection and preventing the already-mounted electronic component from being damaged and to further provide a connection device and method for connection of the wiring board. In addition, the further object of the present invention is to provide a wiring substrate receiving plate capable of allowing a circuit designer to freely select component arrangement and enhancing the component-mounting density and to provide a connection device and connection method for the wiring board.